Lighting apparatus and lighting system with a controller for calculating standby time

ABSTRACT

A lighting apparatus which is one of a plurality of lighting apparatuses each capable of performing wireless communication with a control device. The lighting apparatus includes: a light emitting unit; a controller which controls turn-on of the light emitting unit; and a communication unit configured to perform wireless communication with the control device to obtain correction time from the control device, the correction time being based on communication delay between the control device and each lighting apparatus. The communication unit further obtains a turn-on instruction for turning on the light emitting unit from the control device, and transmits a response to the turn-on instruction to the control device upon obtainment of the turn-on instruction. The controller turns on the light emitting unit after passage of a time period from when the response is transmitted to the device, the time period being calculated by subtracting communication latency from the correction time.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of Japanese PatentApplication Number 2014-182562, filed Sep. 8, 2014, the entire contentof which is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to lighting apparatuses and lightingsystems each capable of performing wireless communication.

2. Description of the Related Art

A conventional technique is available in which turn-on and turn-off of aplurality of lighting apparatuses are controlled by performing wirelesscommunication with the lighting apparatuses. For example, JapaneseUnexamined Patent Application Publication No. 2013-48014 discloses atechnique of transmitting a turn-on instruction using multicast. Thistechnique is intended to simultaneously turn on a plurality of lightingapparatuses.

SUMMARY OF THE INVENTION

However, consideration of communication delay has not been given to thelighting apparatuses according to the above conventional technique. Inother words, even if a control device transmits a turn-on instructionusing multicast, the lighting apparatuses cannot be simultaneouslyturned on due to communication delay between the control device and thelighting apparatuses.

An object of the present disclosure is to provide lighting apparatuseswhich can be simultaneously turned on and a lighting system which iscapable of simultaneously turning on the lighting apparatuses.

In order to achieve the above object, the lighting apparatus accordingto one aspect of the present disclosure is a lighting apparatus which isone of a plurality of lighting apparatuses each capable of performingwireless communication with a device. The lighting apparatus includes: alight emitting unit; a controller which controls turn-on of the lightemitting unit; and a communication unit which performs wirelesscommunication with the device to obtain a correction time from thedevice, the correction time being based on communication delay betweenthe device and each of the plurality of lighting apparatuses. Thecommunication unit further obtains a turn-on instruction for turning onthe light emitting unit from the device, and transmits a response to theturn-on instruction to the device upon obtainment of the turn-oninstruction, and the controller turns on the light emitting unit afterpassage of a time period from when the response is transmitted to thedevice, the time period being calculated by subtracting a communicationlatency from the correction time.

According to the present disclosure, a plurality of lighting apparatusescan be simultaneously turned on.

BRIEF DESCRIPTION OF DRAWINGS

The figures depict one or more implementations in accordance with thepresent teaching, by way of examples only, not by way of limitations. Inthe figures, like reference numerals refer to the same or similarelements.

FIG. 1 schematically illustrates a layout of a plurality of lightingapparatuses in a lighting system according to Embodiment 1 of thepresent disclosure;

FIG. 2 is a block diagram of a functional configuration of the lightingsystem according to Embodiment 1 of the present disclosure;

FIG. 3 illustrates lighting operations of a plurality of lightingapparatuses in a lighting system according to a comparative example ofEmbodiment 1 of the present disclosure;

FIG. 4 illustrates lighting operations of the lighting apparatuses inthe lighting system according to Embodiment 1 of the present disclosure;

FIG. 5 illustrates a relationship between communication distance and ACKreception rate in the use of a wireless signal of 920 MHz band in thelighting system according to Embodiment 1 of the present disclosure;

FIG. 6 illustrates a relationship between communication distance and ACKreception rate in the use of a wireless signal of 2.4 GHz band in thelighting system according to Embodiment 1 of the present disclosure;

FIG. 7A illustrates communication time and received signal strengthindicator (RSSI) relative to communication distance in the lightingsystem according to Embodiment 1 of the present disclosure;

FIG. 7B illustrates communication time and RSSI relative tocommunication distance in the lighting system according to Embodiment 1of the present disclosure;

FIG. 8 is a sequence diagram of calculation processing of correctiontime in the lighting system according to Embodiment 1 of the presentdisclosure;

FIG. 9 is a sequence diagram of simultaneous turn-on processing in thelighting system according to Embodiment 1 of the present disclosure;

FIG. 10 is a sequence diagram of an operation of a lighting systemaccording to Embodiment 2 of the present disclosure;

FIG. 11 is a block diagram of a functional configuration of the lightingsystem according to Embodiment 2 of the present disclosure;

FIG. 12A illustrates an example of a turn-off instruction according toEmbodiment 2 of the present disclosure;

FIG. 12B illustrates an example of a turn-off instruction forretransmission according to Embodiment 2 of the present disclosure;

FIG. 13 is a timing chart of turn-on and turn-off operations in thelighting system according to Embodiment 2 of the present disclosure;

FIG. 14 is a flowchart of an operation of a control device according toEmbodiment 2 of the present disclosure;

FIG. 15 is a flowchart of an operation of each lighting apparatusaccording to Embodiment 2 of the present disclosure;

FIG. 16 is an external perspective view of a lighting apparatusaccording to Embodiment 3 of the present disclosure;

FIG. 17 is a plan view of the lighting apparatus according to Embodiment3 of the present disclosure, viewed from the light emitting side;

FIG. 18 is a cross-sectional view of the lighting apparatus according toEmbodiment 3 of the present disclosure;

FIG. 19 is a plan view of a lighting board according to Embodiment 3 ofthe present disclosure;

FIG. 20 is a perspective view of the lighting board, a reflectivemember, and a light-transmissive member according to Embodiment 3 of thepresent disclosure;

FIG. 21A is a side view, a front view, and a bottom view of a wirelessmodule according to Embodiment 3 of the present disclosure;

FIG. 21B is a side view and a front view of a communication controlboard included in the wireless module according to Embodiment 3 of thepresent disclosure;

FIG. 21C is a block diagram of a configuration of the wireless moduleaccording to Embodiment 3 of the present disclosure;

FIG. 22A is a cross-sectional view of a lighting apparatus according toVariation of Embodiment 3 of the present disclosure;

FIG. 22B is a plan view of a layout of a relay board according toVariation of Embodiment 3 of the present disclosure;

FIG. 23A is a cross-sectional view of a lighting apparatus according toEmbodiment 4 of the present disclosure;

FIG. 23B is a top view of a lighting apparatus according to Embodiment 4of the present disclosure;

FIG. 24 illustrates possible cases assumed in installation of thelighting apparatus according to Embodiment 4 of the present disclosure;

FIG. 25 illustrates return loss of an antenna included in the lightingapparatus according to Embodiment 4 of the present disclosure in the useof a wireless signal of 2.4 GHz band;

FIG. 26 illustrates return loss of an antenna included in a lightingapparatus according to a comparative example of Embodiment 4 of thepresent disclosure in the use of a wireless signal of 2.4 GHz band;

FIG. 27 illustrates return loss of the antenna included in the lightingapparatus according to Embodiment 4 of the present disclosure in the useof a wireless signal of 920 MHz band;

FIG. 28A is a cross-sectional view of a lighting apparatus according toVariation 1 of Embodiment 4 of the present disclosure;

FIG. 28B is a top view of the lighting apparatus according to Variation1 of Embodiment 4 of the present disclosure;

FIG. 29 illustrates return loss of an antenna included in the lightingapparatus according to Variation 1 of Embodiment 4 of the presentdisclosure in the use of a wireless signal of 2.4 GHz band;

FIG. 30 illustrates return loss of the antenna included in the lightingapparatus according to Variation 1 of Embodiment 4 of the presentdisclosure in the use of a wireless signal of 920 MHz band;

FIG. 31 is a cross-sectional view of a lighting apparatus according toVariation 2 of Embodiment 4 of the present disclosure; and

FIG. 32 is a cross-sectional view of a lighting apparatus according toVariation 2 of Embodiment 4 of the present disclosure.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a lighting apparatus and a lighting system according toembodiments of the present disclosure will be described with referenceto the drawings. It should be noted that each of the followingembodiments shows one specific preferred example. The numerical values,shapes, materials, structural elements, the arrangement and connectionof the structural elements etc. shown in the following embodiments aremere examples, and therefore do not limit the present disclosure. Assuch, among the structural elements in the following embodiments,structural elements not recited in any one of the independent claimswhich indicate the broadest concepts of the present disclosure aredescribed as arbitrary structural elements.

Note that the respective figures are schematic diagrams and are notnecessarily precise illustrations. Additionally, similar structuralelements share like reference numbers in the drawings.

Embodiment 1 Lighting System

First, a lighting system according to Embodiment 1 will be brieflydescribed with reference to FIG. 1. FIG. 1 schematically illustrates alayout of a plurality of lighting apparatuses in lighting system 1according to Embodiment 1.

As FIG. 1 illustrates, lighting system 1 includes control device 10 anda plurality of lighting apparatuses 20. Control device 10 performswireless communication with lighting apparatuses 20 to control, forexample, turn-on of lighting apparatuses 20.

Control device 10 is capable of performing wireless communication withlighting apparatuses 20. For example, control device 10 is a mobileinformation terminal such as a remote controller, a smart phone, and apersonal digital assistance (PDA). Control device 10 may be one oflighting apparatuses 20.

Each of lighting apparatuses 20 is capable of performing wirelesscommunication with control device 10, and is, for example, a base light,a ceiling light, a recessed light, and a spotlight. Each lightingapparatus 20 is, for example, located within a 30 m radius from controldevice 10.

In Embodiment 1, control device 10 and lighting apparatuses 20 areconnected in a star topology. Control device 10 corresponds to a hub inthe star topology. The network topology is not limited to the aboveexample, but may be any other topology such as ring, mesh, tree, line,or fully connected topology.

Specifically, as illustrated by solid lines in FIG. 1, control device 10transmits a turn-on instruction to lighting apparatuses 20 usingmulticast. Additionally, as illustrated by a dashed line in FIG. 1,control device 10 receives a response to the turn-on instruction fromeach of lighting apparatuses 20 using unicast.

[Functional Configuration of Lighting System]

Next, a functional configuration of lighting system 1 according toEmbodiment 1 will be described with reference to FIG. 2. FIG. 2 is ablock diagram illustrating a functional configuration of lighting system1 according to Embodiment 1.

[Control Device]

First, a functional configuration of control device 10 will bedescribed.

As FIG. 2 illustrates, control device 10 includes controller 11 andcommunication unit 14. Controller 11 is a processing unit which controlscontrol device 10. Specifically, controller 11 includes commandgenerator 12 and correction time calculator 13.

Controller 11 is formed of, for example, a non-volatile memory such as aread-only memory (ROM) which stores a program (such as an applicationprogram), a central processing unit (CPU) which executes the program, ora volatile memory such as a random access memory (RAM) serving as atemporary working area at the time of execution by the CPU. Controller11 is, for example, a microcontroller.

Command generator 12 generates a turn-on instruction for simultaneouslyturning on lighting apparatuses 20. The turn-on instruction is, forexample, a command for causing each lighting apparatus which hasreceived the turn-on instruction to turn on its light emitting unit. Inother words, the turn-on instruction is not required to include, forexample, information for identifying the lighting apparatus to be turnedon. Each of lighting apparatuses 20 turns on the light emitting unitincluded in lighting apparatus 20, upon receipt of the turn-oninstruction.

Correction time calculator 13 calculates correction time based oncommunication delay between control device 10 and each of lightingapparatuses 20. The correction time is calculated based on thecommunication time between control device 10 and lighting apparatus 20requiring a longest communication time among lighting apparatuses 20. Aspecific method of calculating the correction time will be describedlater. The calculated correction time is transmitted to lightingapparatuses 20 via communication unit 14.

Communication unit 14 is an example of a first communication unit whichperforms wireless communication with lighting apparatuses 20. Forexample, communication unit 14 is a wireless communication module whichperforms wireless communication using ZigBee (registered trademark)which is one of standards of wireless personal area network (WPAN). Thecommunication method used by communication unit 14 is not limited to theabove example. Communication unit 14 may perform communication using awireless local area network (LAN) such as Bluetooth (registeredtrademark) or Wi-Fi (registered trademark). The frequency used in thewireless communication is, for example, a frequency ranging from 421 MHzto 2483.5 MHz, inclusive.

Specifically, communication unit 14 transmits the turn-on instructiongenerated by command generator 12 to lighting apparatuses 20. Here,communication unit 14 transmits the turn-on instruction to lightingapparatuses 20 using multicast. Communication unit 14 also transmits thecorrection time calculated by correction time calculator 13 to lightingapparatuses 20.

Communication unit 14 receives a response to the transmitted turn-oninstruction from each of lighting apparatuses 20. Specifically,communication unit 14 receives an ACK response from each of lightingapparatuses 20 using unicast.

[Lighting Apparatus]

Next, a functional configuration of each lighting apparatus 20 will bedescribed.

As FIG. 2 illustrates, lighting apparatus 20 includes light emittingunit 21, controller 22, communication unit 23, and storage 24.

Light emitting unit 21 is a light-emitting module which includes a lightemitting element, and emits light of a predetermined color (wavelength)such as white. In Embodiment 1, light emitting unit 21 includes, forexample, a housing such as a glass bulb, and a light emitting diode(LED) module disposed in the housing.

The LED module is specifically a chip on board (COB) light emittingmodule in which an LED chip is directly mounted on a board, but the LEDmodule is not limited to the example. For example, the LED module may bea light emitting module which includes a so-called surface mount device(SMD) LED element as a light emitting element. The SMD LED element isspecifically a packaged LED element in which an LED chip is mounted in acavity of a resin molded container which is filled with aphosphor-containing resin. The light emitting element included in lightemitting unit 21 may be, for example, a semiconductor light emittingelement such as a semiconductor laser or any other solid light emittingelement such as an organic electro luminescence (EL) or an inorganic ELelement.

Controller 22 is formed of, for example, a non-volatile memory such as aROM which stores a program (such as an application program), a CPU whichexecutes the program, or a volatile memory such as a RAM serving as atemporary working area at the time of execution by the CPU. Controller22 is, for example, a microcontroller.

Controller 22 controls turn-on of light emitting unit 21. Controller 22may further control turn-off, dimming, and color adjustment of lightemitting unit 21. Controller 22 turns on light emitting unit 21 afterpassage of a time period from when communication unit 23 transmits aresponse. The time period is calculated by subtracting communicationlatency from the correction time. Details of the turn-on control bycontroller 22 will be described later.

Communication unit 23 is an example of a second communication unit whichperforms wireless communication with control device 10. For example,communication unit 23 is a wireless communication module which performswireless communication using ZigBee (registered trademark) which is oneof standards of WPAN. The communication method used by communicationunit 23 is not limited to the above example. Communication unit 23 mayperform communication using a wireless LAN such as Bluetooth (registeredtrademark) or Wi-Fi (registered trademark). The frequency used in thewireless communication is, for example, a frequency ranging from 421 MHzand 2483.5 MHz, inclusive.

Communication unit 23 performs wireless communication with controldevice 10 to obtain correction time from control device 10. The obtainedcorrection time is stored in storage 24 via controller 22. Communicationunit 23 further receives a turn-on instruction from control device 10.The received turn-on instruction is output to controller 22.

Upon receipt of the turn-on instruction, communication unit 23 transmitsa response to the turn-on instruction by performing carrier sense.Specifically, communication unit 23 transmits an ACK response to controldevice 10 by performing carrier sense.

In Embodiment 1, communication unit 23 performs wireless communicationusing only a predetermined frequency. In other words, communication unit23 is prohibited from using so-called frequency-hopping.

Storage 24 is a memory for storing correction time 32 obtained fromcontrol device 10. Storage 24 is, for example, a non-volatile memory.

[Turn-on Operation]

Now, details of turn-on operations in lighting system 1 according toEmbodiment 1 will be described with reference to FIG. 3 and FIG. 4.

FIG. 3 illustrates turn-on operations of lighting apparatuses 20 inlighting system 1 according to a comparative example of Embodiment 1.FIG. 4 illustrates turn-on operations of lighting apparatuses 20 inlighting system 1 according to Embodiment 1.

In the lighting system according to the comparative example, correctiontime is not calculated in advance, and each of lighting apparatuses 20turns on light emitting unit 21 each time lighting apparatus 20 receivesa turn-on instruction. Specifically, each lighting apparatus 20 receivesa turn-on instruction, transmits an ACK response to the received turn-oninstruction, and then turns on light emitting unit 21.

In order to transmit an ACK response to control device 10, each lightingapparatus 20 performs carrier sense to transmit the ACK response at thetransmittable timing. In other words, an ACK response cannot betransmitted while another lighting apparatus 20 is performingcommunication with control device 10.

Accordingly, as FIG. 3 illustrates, each lighting apparatus 20 turns onlight emitting unit 21 after passage of CS latency 30 and turn-onprocessing time 31 from time t0 at which a turn-on instruction isreceived from control device 10 (for example, lighting apparatus A turnson light emitting unit 21 at time t2). CS latency 30 is an example ofcommunication latency, and is latency caused by carrier sense. Turn-onprocessing time 31 is time required for transmitting an ACK response andturning on light emitting unit 21.

In the example in FIG. 3, control device 10 simultaneously transmits aturn-on instruction using multicast at time t0. Hence, lightingapparatuses 20 (lighting apparatuses A to E) approximatelysimultaneously receives the turn-on instruction at time t0, and performscarrier sense attempting to transmit, to control device 10, an ACKresponse indicating the receipt of the turn-on instruction.

As a result of the carrier sense performed by each lighting apparatus20, as FIG. 3 illustrates, lighting apparatus A successfully performscarrier sense at time t1, and turns on light emitting unit 21 at timet2. The rest of lighting apparatuses (lighting apparatuses B to E) whichhave failed in performing carrier sense repeatedly perform carrier sensetill wireless communication is established with control device 10.

At time t2, lighting apparatus A is turned on and wireless communicationbetween lighting apparatus A and control device 10 ends, and thus, next,for example, lighting apparatus C successfully performs carrier sense.Accordingly, lighting apparatus C is turned on at time t3. Subsequently,in a similar manner, lighting apparatus B is turned on at time t4,lighting apparatus D is turned on at time t5, and lighting apparatus Eis turned on at time t6.

In this manner, lighting apparatuses A to E are turned on at differenttimes due to the influence from the latency caused by carrier sense. Inother words, in the lighting system according to the comparativeexample, lighting apparatuses 20 cannot be simultaneously turned on.

In contrast, in Embodiment 1, as FIG. 4 illustrates, each lightingapparatus 20 transmits an ACK response, waits for standby time 41 whichis a time period calculated by subtracting CS latency 30 from correctiontime 32, and turns on light emitting unit 21. Here, correction time 32is specifically a time period from time t0 to time t6. TO is whenlighting apparatus 20, which is turned on last (lighting apparatus E inFIG. 3) among lighting apparatuses 20 to be simultaneously turned on,receives the turn-on instruction. T6 is when lighting apparatus E isactually turned on.

In Embodiment 1, correction time calculator 13 in control device 10calculates correction time 32. Specifically, correction time calculator13 calculates, as correction time 32, a value obtained by subtractingtime t0 at which communication unit 14 transmits the turn-on instructionfrom time t6 at which communication unit 14 receives the last ACKresponse.

Correction time calculator 13 is capable of determining whether thereceived ACK response is the last one or not by, for example,registering the number of lighting apparatuses 20 in advance. In otherwords, as FIG. 4 illustrates, in the case where five lightingapparatuses 20 are to be simultaneously turned on, correction timecalculator 13 is capable of determining that the fifth ACK responsereceived is the last ACK response.

As FIG. 3 and FIG. 4 illustrate, each lighting apparatus 20 hasdifferent CS latency 30. Accordingly, in each lighting apparatus 20,controller 22 calculates standby time 41 based on correction time 32stored in storage 24. Specifically, controller 22 calculates, as standbytime 41, a value obtained by subtracting CS latency 30 from correctiontime 32. CS latency 30 is calculated by subtracting time t0 at which aturn-on instruction is received from the time (such as time t2) at whichcarrier sense is successfully performed.

In each lighting apparatus 20, controller 22 calculates standby time 41each time carrier sense is successfully performed, and waits for standbytime 41 from the time at which carrier sense is successfully performed.Controller 22 turns on light emitting unit 21 after passage of standbytime 41.

In this manner, as FIG. 4 illustrates, lighting apparatuses 20 iscapable of simultaneously turning on light emitting units 21 at time t6.

[Communication Distance and Success Rate of ACK Response]

Subsequently, a relationship between communication distance and successrate of ACK response in lighting system 1 according to Embodiment 1 willbe described with reference to FIG. 5 and FIG. 6.

FIG. 5 illustrates a relationship between communication distance and ACKreception rate in the use of a wireless signal of 920 MHz band inlighting system 1 according to Embodiment 1. FIG. 6 illustrates arelationship between communication distance and ACK reception rate inthe use of a wireless signal of 2.4 GHz band in lighting system 1according to Embodiment 1.

In FIG. 5 and FIG. 6, the horizontal axes indicate communicationdistance, and vertical axes indicate ACK reception rate. Thecommunication distance is a distance between control device 10 andlighting apparatus 20. The ACK reception rate is a rate at which controldevice 10 has received ACK responses using unicast to a broadcastedcommand, that is, a rate of successful communication.

As FIG. 5 illustrates, in the case of wireless communication using afrequency of 920 MHz, the ACK reception rate tends to decrease with anincrease in communication distance. This tendency does not depend ondata length. As FIG. 6 illustrates, in the case of wirelesscommunication using a frequency of 2.4 GHz, too, the ACK reception ratetends to decrease with an increase in communication distance.

In the case of the frequency of 2.4 GHz, however, the ACK reception rateis approximately 100% when the communication distance ranges from 0 m to20 m. When the communication distance exceeds 30 m, the ACK receptionrate significantly decreases. Hence, in lighting system 1 according toEmbodiment 1, making the communication distance less than or equal to 30m leads to an ACK reception rate greater than or equal to 90%approximately, resulting in an increase in communication accuracy.Specifically, in Embodiment 1, it may be that the distance betweencontrol device 10 and each lighting apparatus 20 is less than or equalto 30 m. It is preferable that the frequency used in wirelesscommunication is greater than or equal to 2.4 GHz.

In lighting system 1 according to Embodiment 1, the frequency of 920 MHzband can also be used in wireless communication. In this case, as FIG. 5illustrates, shorter communication distance is preferable in the use offrequency of 920 MHz band because the ACK reception rate decreases moresignificantly with an increase in communication distance than the caseof the frequency of 2.4 GHz band.

For example, the communication distance can be reduced by connectingcontrol device 10 and lighting apparatuses 20 in a mesh topology insteadof start topology. In other words, communication unit 23 in eachlighting apparatus 20 may be capable of performing wirelesscommunication with another lighting apparatus 20. With this, lightingapparatus 20 located far from control device 10 is capable of performingaccurate communication with control device 10 by being routed throughnearby another lighting apparatus 20.

[Communication Distance and Communication Time]

Subsequently, reproducibility of a relationship between communicationdistance and communication time in lighting system 1 according toEmbodiment 1 will be described with reference to FIG. 7A and FIG. 7B.

FIG. 7A and FIG. 7B each illustrate communication time and receivedsignal strength relative to communication distance in the lightingsystem according to Embodiment 1.

In FIG. 7A and FIG. 7B, the horizontal axes indicate communicationdistance, and vertical axes indicate communication time and receivedsignal strength indicator (RSSI). The communication distance is adistance between control device 10 and lighting apparatus 20. Thecommunication time is a time period taken from when control device 10transmits a command to when control device 10 receives an ACK response.Here, the transmitting a command and receiving an ACK response wereperformed using unicast. The RSSI indicates the strength of radio waveswhen a wireless signal transmitted from control device 10 is received.

FIG. 7A shows average values of the communication time and the RSSIobtained when data of 100 bytes was successively transmitted 100 timesin one cycle. FIG. 7B shows average values of the communication time andthe RSSI obtained when data of 100 bytes was successively transmitted100 times in two cycles.

As FIG. 7A and FIG. 7B illustrate, the RSSI tends to decrease with anincrease in communication distance, but the reproducibility thereof islow. For example, in FIG. 7A, the RSSI increases when the communicationdistance is 30 m and 37 m, whereas in FIG. 7B, the RSSI decreases whenthe communication distance is 30 m and 37 m.

On the other hand, as FIG. 7A and FIG. 7B illustrate, the communicationtime tends to gradually increase when the communication distance rangesfrom 0 m to 30 m, and significantly increases when the communicationdistance exceeds 30 m. In such a manner, approximately the same tendencycan be seen relative to the communication time in both FIG. 7A and FIG.7B, and its reproducibility is high.

Accordingly, as described above, by using the correction time calculatedbased on the communication time, turn-on of lighting apparatuses 20 canbe accurately controlled.

[Operation of Lighting System]

Next, an operation of lighting system 1 according to Embodiment 1 willbe described.

The operation of lighting system 1 according to Embodiment 1 includescalculation processing of correction time and simultaneous turn-onprocessing using the calculated correction time. In the followingdescription, first, calculation processing of correction time will bedescribed with reference to FIG. 8.

[Calculation Processing of Correction Time]

FIG. 8 is a sequence diagram of calculation processing of correctiontime in lighting system 1 according to Embodiment 1. Here, a descriptionis given of an example where lighting system 1 includes control device10 and three lighting apparatuses 20 a to 20 c.

First, control device 10 transmits a turn-on instruction to lightingapparatuses 20 a to 20 c (S10). Specifically, command generator 12generates a turn-on instruction, and communication unit 14 transmits thegenerated turn-on instruction to lighting apparatuses 20 a to 20 c usingmulticast.

Each of lighting apparatuses 20 a to 20 c receives the turn-oninstruction, and performs carrier sense to transmit an ACK response(S20). As a result, for example, lighting apparatus 20 a successfullyperforms carrier sense, and transmits an ACK response to control device10 (S20 a). Lighting apparatus 20 a then turns on light emitting unit 21(S22 a). At this point, since correction time has not been calculatedyet, and has not been stored in storage 24 of lighting apparatus 20 a,lighting apparatus 20 a turns on light emitting unit 21 immediatelyafter completion of transmission of the ACK response.

Next, lighting apparatus 20 b successfully performs carrier sense, andtransmits an ACK response to control device 10 (S20 b). Lightingapparatus 20 b then turns on light emitting unit 21 (S22 b).

Next, lighting apparatus 20 c successfully performs carrier sense, andtransmits an ACK response to control device 10 (S20 c). Lightingapparatus 20 c then turns on light emitting unit 21 (S22 c).

Next, control device 10 calculates correction time (S12). Specifically,correction time calculator 13 calculates correction time based oncommunication delay between control device 10 and respective lightingapparatuses 20 a to 20 c. For example, correction time calculator 13calculates, as correction time, a difference between the time at whichthe turn-on instruction was transmitted and the time at which the lastACK response was received.

Next, control device 10 transmits the calculated correction time tolighting apparatuses 20 a to 20 c (S14). Specifically, communicationunit 14 transmits the calculated correction time to lighting apparatuses20 a to 20 c using multicast.

Each of lighting apparatuses 20 a to 20 c receives the correction time,and stores the received correction time into storage 24 (S24).

By causing each lighting apparatus 20 a to 20 c to store the correctiontime into storage 24 as described above, simultaneous turn-on can beperformed using the correction time upon receipt of a subsequent turn-oninstruction.

[Simultaneous Turn-on Processing]

Next, simultaneous turn-on processing will be described with referenceto FIG. 9. FIG. 9 is a sequence diagram of simultaneous turn-onprocessing in lighting system 1 according to Embodiment 1.

First, control device 10 transmits a turn-on instruction to lightingapparatuses 20 a to 20 c (S10). Specifically, command generator 12generates a turn-on instruction, and communication unit 14 transmits thegenerated turn-on instruction to lighting apparatuses 20 a to 20 c usingmulticast.

Each of lighting apparatuses 20 a to 20 c receives the turn-oninstruction, and performs carrier sense to transmit an ACK response(S20). As a result, for example, lighting apparatus 20 a successfullyperforms carrier sense, and transmits an ACK response to control device10 (S20 a). Lighting apparatus 20 a then waits without turning on lightemitting unit 21 (S26 a). Specifically, controller 22 calculates standbytime 41 based on the correction time and the time at which the ACKresponse was transmitted, and waits without turning on light emittingunit 21 till passage of standby time 41 from the time at which the ACKresponse was transmitted.

Next, lighting apparatus 20 b successfully performs carrier sense, andtransmits an ACK response to control device 10 (S20 b). Lightingapparatus 20 b calculates standby time 41 and waits in a similar mannerto lighting apparatus 20 a (S26 b).

Next, lighting apparatus 20 c successfully performs carrier sense, andtransmits an ACK response to control device 10 (S20 c). Lightingapparatus 20 c calculates standby time 41 and waits (S26 c).

Each of lighting apparatuses 20 a to 20 c turns on light emitting unit21 after passage of its own standby time 41 (S28). Each standby time 41is a different value depending on the time at which the ACK response wastransmitted as illustrated in FIG. 4. Specifically, standby time 41 iscalculated such that light emitting unit 21 is turned on after passageof the correction time from when control device 10 transmitted theturn-on instruction. Accordingly, as FIG. 4 illustrates, lightingapparatuses 20 a to 20 c can be simultaneously turned on.

[Conclusion]

As described above, lighting apparatus 20 according to Embodiment 1 isone of a plurality of lighting apparatuses 20 each capable of performingwireless communication with control device 10. Lighting apparatus 20includes light emitting unit 21; controller 22 which controls turn-on oflight emitting unit 21; and communication unit 23 which performswireless communication with control device 10 to obtain, from controldevice 10, correction time which is based on communication delay betweencontrol device 10 and each lighting apparatus 20. Communication unit 23further obtains a turn-on instruction for turning on light emitting unit21 from control device 10, and upon obtainment of the turn-oninstruction, transmits a response to the turn-on instruction to controldevice 10. Controller 22 turns on light emitting unit 21 after passageof a time period from when the response was transmitted to controldevice 10. The time period is calculated by subtracting communicationlatency from the correction time.

Accordingly, since each light emitting unit 21 is turned on afterpassage of a time period calculated by subtracting each communicationlatency from the correction time, all lighting apparatuses 20 can besimultaneously turned on.

For example, control device 10 and lighting apparatuses 20 are connectedin a star topology. Control device 10 transmits a turn-on instruction tolighting apparatuses 20 using multicast. Communication unit 23 performscarrier sense to transmit a response to control device 10. Communicationlatency is latency caused by carrier sense.

With this, since information indicating receipt of the turn-oninstruction (specifically, an ACK response) is transmitted by performingcarrier sense, latency due to carrier sense occurs when there are aplurality of lighting apparatuses 20. Accordingly, in such a case, theadvantageous effects produced by turn-on control using the correctiontime according to Embodiment 1 can be more effectively used.

Moreover, for example, communication unit 23 is capable of performingwireless communication with another one of lighting apparatuses 20.

Accordingly, even if a distance between control device 10 and lightingapparatus 20 is long, wireless communication can be performed usinganother lighting apparatus 20 located therebetween.

Moreover, for example, lighting apparatuses 20 are, for example, locatedwithin a 30 m radius from control device 10.

With this, accurate wireless communication can be performed betweencontrol device 10 and lighting apparatuses 20.

Moreover, for example, the correction time is calculated based on thecommunication time between control device 10 and lighting apparatus 20requiring the longest communication time among lighting apparatuses 20.

With this, the correction time is calculated based on the longestcommunication time. Hence, control can be performed such that all oflighting apparatuses 20 have completed wireless communication at thetiming at which lighting apparatuses 20 are to be simultaneously turnedon. In other words, lighting apparatuses 20 can be simultaneously turnedon more reliably.

Moreover, for example, communication unit 23 performs wirelesscommunication using only a predetermined frequency.

With this, since so-called frequency-hopping is prohibited, wirelesscommunication cannot be performed using another frequency even ifcarrier sense fails. In other words, one or more lighting apparatuses 20always have latency caused by carrier sense, which prohibits lightingapparatuses 20 from being simultaneously turned on.

However, since lighting apparatuses 20 according to Embodiment 1 performturn-on control using correction time, lighting apparatuses 20 can besimultaneously turned on. Accordingly, when the frequency-hopping isprohibited, the advantageous effects produced by turn-on control usingthe correction time according to Embodiment 1 can be more effectivelyused.

Moreover, for example, communication unit 23 performs wirelesscommunication using a frequency ranging from 421 MHz to 2483.5 MHz,inclusive.

With this, for example, wireless communication can be performed using afrequency band permitted in Japan.

Moreover, for example, lighting system 1 according to Embodiment 1includes control device 10 and a plurality of lighting apparatuses 20each capable of performing wireless communication with control device10. Control device 10 includes correction time calculator 13 whichcalculates correction time which is based on communication delay betweencontrol device 10 and each lighting apparatus 20; and communication unit14 which performs wireless communication with lighting apparatuses 20 totransmit, to lighting apparatuses 20, the correction time and a turn-oninstruction for turning on lighting apparatuses 20. Each of lightingapparatuses 20 includes light emitting unit 21, controller 22 whichcontrols turn-on of light emitting unit 21, and communication unit 23which obtains the correction time and the turn-on instruction fromcontrol device 10, and upon obtainment of the turn-on instruction,transmits a response to the turn-on instruction to control device 10.Controller 22 turns on light emitting unit 21 after passage of a timeperiod from when the response was transmitted to control device 10. Thetime period is calculated by subtracting communication latency from thecorrection time.

Accordingly, since each light emitting unit 21 is turned on afterpassage of a time period calculated by subtracting each communicationlatency from the correction time, all lighting apparatuses 20 can besimultaneously turned on.

Embodiment 2

Next, a lighting apparatus and a lighting system according to Embodiment2 will be described.

FIG. 10 is a sequence diagram of an operation of lighting system 100according to Embodiment 2. FIG. 11 is a block diagram of a functionalconfiguration of lighting system 100 according to Embodiment 2. Lightingsystem 100 includes control device 110 and a plurality of lightingapparatuses 120. Controller 110 and lighting apparatuses 120respectively correspond to control device 10 and lighting apparatuses 20according to Embodiment 1.

[Control Device]

First, a configuration of control device 110 will be described.

As FIG. 10 illustrates, control device 110 includes, for example, tabletterminal 110 a, wireless LAN 110 b, and bridge 110 c. A command such asa turn-on instruction or a turn-off instruction is transmitted fromtablet terminal 110 a to lighting apparatuses 120 via wireless LAN 110 band bridge 110 c. A response such as ACK response transmitted from eachof lighting apparatuses 120 is transmitted to tablet terminal 110 a viabridge 110 c and wireless LAN 110 b.

Here, a functional configuration of control device 110 will be describedwith reference to FIG. 11.

As FIG. 11 illustrates, control device 110 is different from controldevice 10 illustrated in FIG. 2 in that command generator 112 isincluded instead of command generator 12.

Command generator 112 generates a turn-off instruction in addition tothe functions of command generator 12. Depending on the communicationstatus, it may be that the command transmitted from control device 110is not properly received by lighting apparatuses 120, or that the ACKresponse transmitted from each lighting apparatuses 120 is not properlyreceived by control device 110. In order to deal with such cases,command generator 112 generates a command for retransmission.Specifically, command generator 112 generates a turn-off instruction forretransmission.

Controller 11 corresponds to tablet terminal 110 a, and communicationunit 14, for example, corresponds to wireless LAN 110 b and bridge 110c.

As FIG. 10 illustrates, bridge 110 c transmits a command such as aturn-on instruction or a turn-off instruction to lighting apparatuses120 a to 120 d using broadcast. When each of lighting apparatuses 120 ato 120 d receives the command, each of lighting apparatus 120 a to 120 dtransmits an ACK response to the command to bridge 110 c using unicast.

Here, for example, one of lighting apparatuses 120 may fail to properlyreceive the command. Alternatively, bridge 110 c may fail to properlyreceive the ACK response transmitted from each lighting apparatus 120.In such a case, control device 110 cannot receive the ACK response, andthus, generates and transmits a command for retransmission after apredetermined period.

Such failures in receiving a command or transmitting an ACK responsehappen due to the surrounding environment. In practice, an idealenvironment where waves from control device 110 reaches directly andwhich is favorable for communication is rare due to obstructions such asbuilding structures, building materials, furniture or home electronicsin the room. Actual environment includes areas where radio waves arelikely to reach and areas where radio waves are unlikely to reach, dueto reflected waves, transmitted waves, diffracted waves, and the like.This may cause failure of transmission and reception of a command or anACK response.

[Lighting Apparatus]

Next, a configuration of lighting apparatus 120 will be described.

As FIG. 11 illustrates, lighting apparatus 120 is different fromlighting apparatus 20 illustrated in FIG. 2 in that controller 122 isincluded instead of controller 22.

Controller 122 is formed of, for example, a non-volatile memory such asa ROM which stores a program (such as an application program), a CPUwhich executes the program, or a volatile memory such as a RAM servingas a temporary working area at the time of execution by the CPU.Controller 122 is, for example, a microcontroller.

Controller 122 includes lighting controller 125 and speed calculator126.

Lighting controller 125 controls turn-on and turn-off of light emittingunit 21. In Embodiment 2, lighting controller 125 controls turn-on andturn-off of light emitting unit 21 based on the turn-on instruction andthe turn-off instruction received by communication unit 23 such thatdimming rate of light emitting unit 21 becomes a predetermined value(“100” (turn-on) or “0” (turn-off)) at a predetermined speed. Forexample, lighting controller 125 performs turn-off control of lightemitting unit 21 such that the dimming rate of light emitting unit 21becomes “0” from “100” in 3 to 5 seconds, when communication unit 23receives a turn-off instruction. When communication unit 23 receives aturn-off instruction for retransmission, lighting controller 125performs turn-off control of light emitting unit 21 such that thedimming rate becomes “0” at the speed calculated by speed calculator126.

Lighting controller 125 performs turn-on control of light emitting unit21 based on correction time, for example, in a similar manner toEmbodiment 1. Specific processing is the same as the one described inEmbodiment 1.

Speed calculator 126 calculates turn-off speed of light emitting unit21. The turn-off speed is, specifically, a speed at which the dimmingrate of light emitting unit 21 which is on is changed to “0”. Forexample, speed calculator 126 determines a time period taken to turn offlight emitting unit 21, divides the current value of the dimming rate oflight emitting unit 21 which is on by the determined time, andcalculates turn-off speed. The time period taken to turn off lightemitting unit 21 is determined based on the turn-off instruction forretransmission received by communication unit 23.

[Turn-Off Instruction]

Here, the turn-off instruction according to Embodiment 2 will bedescribed referring to FIG. 12A and FIG. 12B. FIG. 12A illustratesturn-off instruction 130 according to Embodiment 2. FIG. 12B illustratesturn-off instruction for retransmission 140 according to Embodiment 2.

As FIG. 12A illustrates, turn-off instruction 130 includes turn-offcommand 131.

Turn-off command 131 is a command for causing lighting apparatus 120 toturn off light emitting unit 21. Lighting controller 125 performsturn-off control of light emitting unit 21 at a predetermined speed uponreceipt of turn-off instruction 130.

As FIG. 12B illustrates, turn-off instruction for retransmission 140includes turn-off command 131 and delay time information 141.

Delay time information 141 indicates delay time taken before turn-offinstruction for retransmission 140 is transmitted. Specifically, delaytime information 141 indicates, as delay time, a time period taken fromwhen turn-off instruction 130 is transmitted to when turn-offinstruction for retransmission 140 is transmitted.

Accordingly, when lighting apparatus 120 receives turn-off instructionfor retransmission 140, speed calculator 126 is capable of calculatingthe turn-off speed based on delay time information 141.

Specifically, first, speed calculator 126 calculates time required tonormally turn off light emitting unit 21, based on the normal turn-offspeed and the current dimming rate of light emitting unit 21. The normalturn-off speed is a predetermined speed, and is, specifically, a speedat which light emitting unit 21 is turned off when turn-off instruction130 transmitted first is received.

Next, speed calculator 126 calculates the remaining time beforeturn-off, by subtracting the time indicated by delay time information141 from the time required to normally turn-off light emitting unit 21.Lastly, speed calculator 126 calculates the turn-off speed by dividingthe current dimming rate of light emitting unit 21 by the remainingtime.

[Turn-Off Control]

The following describes turn-off control performed when turn-offinstruction for retransmission 140 is received, with reference to FIG.13.

FIG. 13 is a timing chart of turn-on and turn-off operations in lightingsystem 100 according to Embodiment 2. In FIG. 13, the horizontal axisindicates time, and the vertical axis indicates the dimming rate oflight emitting unit 21 in each lighting apparatus.

Lighting apparatuses 120 a to 120 c each receive turn-off instruction130 from control device 110 at time t20. Each of lighting apparatuses120 a to 120 c performs turn-off control of light emitting unit 21 at apredetermined speed (at normal speed) based on turn-off instruction 130.Accordingly, from time t20 to time t22, the dimming rate of each lightemitting unit 21 decreases at a predetermined speed.

On the other hand, lighting apparatus 120 d cannot receive turn-offinstruction 130 properly at time t20, and receives turn-off instructionfor retransmission 140 at time t21.

Here, when speed calculator 126 does not calculate the turn-off speed,lighting apparatus 120 d performs turn-off control of light emittingunit 21 at a predetermined speed based on turn-off instruction forretransmission 140. Accordingly, from time t21 to time t24, the dimmingrate of light emitting unit 21 decreases at a predetermined speed.

In such a manner, lighting apparatus 120 d is turned off at differenttime from lighting apparatuses 120 a to 120 c.

In contrast, in Embodiment 2, speed calculator 126 calculates turn-offspeed. Specifically, speed calculator 126 calculates the remaining timebased on delay time information 141 included in turn-off instruction forretransmission 140, and determines the turn-off speed such that thedimming rate of light emitting unit 21 becomes “0” in the calculatedremaining time. For example, the delay time indicated by delay timeinformation 141 is a time period between time t20 and time t21, and theremaining time is a time period between time t21 and time t22.

As described in Embodiment 1, too, lighting apparatuses 120 havedifferences in latency caused by carrier sense. The differencecorresponds to the time period between time t22 and time t23 illustratedin FIG. 13, and is, for example, less than or equal to 100 ms.Accordingly, when speed calculator 126 calculates the remaining time,time t23 may be used instead of time t22.

As described above, in Embodiment 2, light emitting unit 21 is turnedoff based on the turn-off speed calculated by speed calculator 126, andthus, as FIG. 13 illustrates, turn-off time of each of lightingapparatuses 120 a to 120 d is substantially the same. In other words,lighting apparatuses 120 a to 120 d can be simultaneously turned off.

Although turn-off control has been described above, turn-on control maybe performed in a similar manner. In other words, speed calculator 126calculates turn-on speed in a similar manner to turn-off speed uponreceipt of a turn-on instruction for retransmission, and lightingcontroller 125 is capable of performing turn-on control of lightemitting unit 21 based on the calculated turn-on speed.

Accordingly, for example, although FIG. 13 illustrates an example wherelighting apparatus 120 d is turned on at time t14, lighting apparatus120 d can be turned on between time t12 and time t13 based on thecalculated turn-on speed. Hence, lighting apparatuses 120 a to 120 d canbe simultaneously turned on.

[Operation of Control Device]

Next, an operation of lighting system 100 according to Embodiment 2 willbe described.

First, an operation of control device 110 according to Embodiment 2 willbe described with reference to FIG. 14. FIG. 14 is a flowchart of anoperation of control device 110 according to Embodiment 2.

First, command generator 112 generates turn-off instruction 130, andtransmits generated turn-off instruction 130 via communication unit 14(S110). Specifically, communication unit 14 transmits turn-offinstruction 130 generated by command generator 112 to lightingapparatuses 120 using multicast.

Next, command generator 112 determines whether or not communication unit14 has received responses to turn-off instruction 130 from lightingapparatuses 120 within a predetermined period (S112). Specifically,command generator 112 determines whether or not responses from all oflighting apparatuses 120 have been received.

When responses from one or more lighting apparatuses 120 have not beenreceived (No in S112), command generator 112 generates turn-offinstruction for retransmission 140, and transmits turn-off instructionfor retransmission 140 via communication unit 14 (S114). For example,communication unit 14 transmits turn-off instruction for retransmission140 only to lighting apparatus 120 from which a response has not beenreceived.

After transmission of turn-off instruction for retransmission 140,command generator 112 determines whether or not a response has beenreceived within a predetermined period. Subsequently, transmission ofturn-off instruction for retransmission 140 (S114) is repeated till aresponse is received.

When responses from all of lighting apparatuses 120 have been received(Yes in S112), the operation of control device 110 ends.

[Operation of Lighting Apparatus]

Subsequently, an operation of lighting apparatus 120 according toEmbodiment 2 will be described with reference to FIG. 15. FIG. 15 is aflowchart of an operation of lighting apparatus 120 according toEmbodiment 2.

First, lighting controller 125 receives turn-off instruction viacommunication unit 23 (S120). Controller 122 transmits an ACK responseto the turn-off instruction to control device 110 via communication unit23.

Lighting controller 125 determines whether or not the received turn-offinstruction is a retransmitted turn-off instruction (S122).Specifically, lighting controller 125 determines whether or not thereceived turn-off instruction includes delay time information 141. Whendelay time information 141 is included, the turn-off instruction is theretransmitted turn-off instruction.

When the received turn-off instruction is not the retransmitted turn-offinstruction (No in S122), that is, when the turn-off instructiontransmitted first is received, light emitting unit 21 is turned off at apredetermined normal turn-off speed (S126).

When the received turn-off instruction is the retransmitted turn-offinstruction (Yes in S122), speed calculator 126 calculates the turn-offspeed (S124). Specifically, as described above, speed calculator 126calculates delay time using delay time information 141 included in theturn-off instruction for retransmission. Subsequently, lightingcontroller 125 turns off light emitting unit 21 at the speed calculatedby speed calculator 126 (S126).

When the turn-off instruction for retransmission is received in such amanner, that is, when the turn-off instruction transmitted first has notbeen received, speed calculator 126 calculates turn-off speed so as tomatch the turn-off time of other lighting apparatuses 120 (time at whichthe dimming rate becomes “0”). In this way, lighting system 100according to Embodiment 2 is capable of simultaneously turning offlighting apparatuses 120.

[Conclusion]

As described above, in lighting system 100 according to Embodiment 2,each lighting apparatus 120 includes speed calculator 126 whichcalculates turn-off speed upon receipt of a turn-off instruction forretransmission.

With this, when a lighting apparatus receives a turn-off instruction forretransmission, the lighting apparatus finds out that turn-offpreparation is delayed compared to the other lighting apparatuses.Hence, by calculating the turn-off speed which is faster than the normalturn-off speed, the lighting apparatus can be turned on together withthe turn-off of the other lighting apparatuses. Accordingly, Embodiment2 allows lighting apparatuses 120 to be simultaneously turned off.

Embodiment 3

Next, a lighting apparatus according to Embodiment 3 will be described.

[Lighting Apparatus]

FIG. 16 is an external perspective view of lighting apparatus 200 (LEDlamp) according to Embodiment 3. Specifically, FIG. 16 is a perspectiveview of lighting apparatus 200 viewed from below at an oblique angle.

In FIG. 16, the dashed line indicates lamp axis J of lighting apparatus200. In Embodiment 3, lamp axis J is an axis serving as the center ofrotation (axis of rotation) when lighting apparatus 200 (LED lamp) isattached to a socket of a lighting fixture. Lamp axis J corresponds tothe central axis of a base of the LED lamp and the central axis of thesocket of the lighting fixture.

As FIG. 16 illustrates, lighting apparatus 200 according to Embodiment 3is a thin flat LED unit having an overall discus or low-profile shape.Lighting apparatus 200 has an outer chassis including light-transmissivemember 230, housing 240, and support base 250. Lighting apparatus 200has a base configured, for example, as a GX53 base or a GH76p base.

In Embodiment 3, the light emitting side refers to the side from whichlight is emitted, and is the side of lighting apparatus 200 from whichlight is taken out. In FIG. 16, the light emitting side is the downside.

FIG. 17 is a plan view of lighting apparatus 200 according to Embodiment3 viewed from the light emitting side. FIG. 18 is a cross-sectional viewof lighting apparatus 200 according to Embodiment 3. Specifically, FIG.18 illustrates a cross section of lighting apparatus 200 taken along aline passing through the center of lighting apparatus 200 (cross sectiontaken along line A-A in FIG. 17).

As FIG. 17 and FIG. 18 illustrate, lighting apparatus 200 includes lightemitting unit 210, reflective member 220, light-transmissive member 230,housing 240, support base 250, lighting board 260, and wireless module270. In FIG. 17, light-transmissive member 230 is omitted in order tofacilitate visualization of inside of housing 240.

The following provides detailed descriptions of each structural memberincluded in lighting apparatus 200, with reference to FIG. 17, FIG. 18,FIG. 19, and FIG. 20.

FIG. 19 is a plan view of lighting board 260 according to Embodiment 3.FIG. 20 is a perspective view of lighting board 260, reflective member220, and light-transmissive member 230 according to Embodiment 3.

[Light Source]

Light emitting unit 210 is a light source of lighting apparatus 200, andis disposed inside housing 240. Light emitting unit 210 is, for example,a light emitting module which includes a light emitting element, andemits light of a predetermined color (wavelength) such as white.

As FIG. 18 illustrates, light emitting unit 210 includes board 211 andLED 212. For example, light emitting unit 210 is a COB LED moduleincluding board 211 with a directly mounded bare chips (LEDs 212).Although not illustrated, a metal line having a predetermined shape andfor electrically connecting LEDs 212, a terminal for receiving power forturning on LEDs 212, and the like are disposed on board 211.

For example, a ceramic board, a resin board, or a metal based board maybe used as board 211. Board 211 may have any shape, such as rectangularshape, polygon shape, round shape in a plan view.

Each LED 212 is an example of the light emitting element, and is asemiconductor light emitting element which emits light in response topredetermined power. In Embodiment 3, LED 212 is a bare chip which emitsmonochromatic visible light, and is, for example, a blue LED chip whichemits blue light. A plurality of LEDs 212 are, for example, mountedalong multiple lines or in a matrix on board 211, and sealed by asealing member (not illustrated).

The sealing member is made from, for example, a resin material, and isformed so as to collectively seal LEDs 212. For example, the sealingmember may be linearly formed so as to form each line of LEDs 212, ormay be formed in a round or rectangle shape so as to collectively sealLEDs 212.

The sealing member is mainly made from, for example, alight-transmissive material, and includes a phosphor as a wavelengthconverting material. For example, the sealing member includes YAG basedyellow phosphor particles, and is excited by blue light emitted fromLEDs 212 and emits yellow light. Accordingly, the sealing member emitswhite light as a combined light of the yellow light resulting fromexcitation and the blue light from LEDs 212.

Light emitting unit 210 is disposed on a predetermined surface.Specifically, as FIG. 18 illustrates, light emitting unit 210 isdisposed on and fixed to support base 250. For example, light emittingunit 210 and support base 250 may be fixed by applying adhesive betweensupport base 250 and the back surface of board 211 (the surface oppositeto the surface on which LEDs 212 are mounted).

[Reflective Member]

Reflective member 220 is disposed in housing 240, and reflects lightemitted from light emitting unit 210. As FIG. 18 illustrates, reflectivemember 220 includes truncated conical part 221 and circular part 222.

Truncated conical part 221 is a part having an approximately truncatedconical shape, and includes entrance opening 223 and exit opening 224.The internal diameter and the external diameter of truncated conicalpart 221 gradually increase from entrance opening 223 toward exitopening 224.

Entrance opening 223 is an opening where light emitted from lightemitting unit 210 enters. Exit opening 224 is an opening where lightentered entrance opening 223 exits. An end portion of truncated conicalpart 221 on entrance opening 223 side is configured so as to surroundthe light emitting region of light emitting unit 210. In other words,the area of entrance opening 223 is greater than or approximately thesame as the light emitting region of light emitting unit 210. The areaof exit opening 224 is not particularly limited. For example, the rangeilluminated by light can be increased by increasing the area of exitopening 224. On the other hand, the range illuminated by light can bedecreased by reducing the area of exit opening 224.

Truncated conical part 221 includes reflective surface 225 whichreflects light emitted from light emitting unit 210. Specifically, theinner surface of truncated conical part 221 is reflective surface 225.

As FIG. 20 illustrates, truncated conical part 221 includes through-hole226. Through-hole 226 is a hole for inserting wireless module 270. Theshape of through-hole 226, for example, depends on the shape of wirelessmodule 270, and is rectangle.

Circular part 222 is a part having an approximately annular shape, andincludes a plurality of recesses 227 on its outer ends. Recesses 227 areengaged with claw parts 232 of light-transmissive member 230.Accordingly, when light-transmissive member 230 is rotated, reflectivemember 220 also rotates in accordance with the rotation oflight-transmissive member 230. In other words, the position ofreflective member 220 is changeable in housing 240.

Reflective member 220 is not always required to include circular part222. In other words, since exit opening 224 is larger when circular part222 is not included, the range illuminated by light can be increased.

Reflective member 220 is, for example, made from a hard white resinmaterial having electrically insulating properties. In order to improvereflectance, reflective surface 225 may be formed on the internalsurface of resin reflective member 220 (truncated conical part 221) bycoating a metal deposition film made from a metal material such assilver or aluminum. Alternatively, reflective member 220 may be entirelyformed using a metal material such as aluminum.

[Light-Transmissive Member]

Light-transmissive member 230 is made from a light-transmissive materialso as to allow light emitted from light emitting unit 210 to be takenout. For example, light-transmissive member 230 is made from a resinmaterial such as acrylic resin (PMMA) or polycarbonate (PC).Light-transmissive member 230 may be transparent having no lightdiffusion properties (the internal structure is viewable), or may havelight diffusion properties. For example, an opalescent light diffusingfilm can be formed by depositing, on the internal or external surface oflight-transmissive member 230, a resin including a light diffusingmaterial such as silica or calcium carbonate, or a white pigment.

As FIG. 20 illustrates, light-transmissive member 230 includes platepart 231 and claw parts 232.

Plate part 231 has an approximately circular shape. As FIG. 18illustrates, plate part 231 is disposed so as to cover exit opening 224while being in contact with circular part 222 of reflective member 220.The portion, of plate part 231, which covers exit opening 224 (centralportion), for example, has an approximately even thickness, whereas theportion, of plate part 231, which contacts circular part 222(surrounding portion) has a thickness which decreases toward theperipheral portion.

Claw parts 232 are disposed upright on the peripheral portion of platepart 231. Claw parts 232 are engaged with recesses 227 of reflectivemember 220. Claw parts 232 may have any shape.

[Housing]

Housing 240 houses light emitting unit 210, and, as FIG. 18 illustrates,includes larger-diameter part 241 and smaller-diameter part 242.Larger-diameter part 241 is a thin part having an approximately circulartube shape, and has inner and external diameters larger thansmaller-diameter part 242. Smaller-diameter part 242 is a thin parthaving an approximately circular tube shape, and has inner and externaldiameters smaller than larger-diameter part 241. Larger-diameter part241 and smaller-diameter part 242 are integrally formed.

Housing 240 is made from, for example, a resin material havingelectrically insulating properties, such as polybutylene terephthalate(PBT). Housing 240 may be made from metal instead of resin.

As FIG. 18 illustrates, light emitting unit 210, reflective member 220,lighting board 260, and wireless module 270 are disposed inside housing240. Specifically, light emitting unit 210 is disposed insmaller-diameter part 242, and reflective member 220, lighting board260, and wireless module 270 are disposed in larger-diameter part 241.Moreover, housing 240 includes support base 250 so as to cover theopening on the smaller-diameter part 242 side, and includeslight-transmissive member 230 so as to cover the opening on thelarger-diameter part 241 side.

[Support Base]

Support base 250 is a support member which supports light emitting unit210 and housing 240. Support base 250 also functions as a heat sink thatdissipates heat generated by light emitting unit 210. As such, supportbase 250 preferably includes a metal material such as aluminum or aresin material having a high rate of thermal conductivity.

Support base 250 also functions as a predetermined base connected to alighting fixture (not illustrated) together with housing 240 and powersupply terminals 263 of lighting board 260. Lighting apparatus 200includes a standardized base structure which complies with a socket ofthe lighting fixture. Examples of such a base structure include, asdescribed above, a GX53 base or a GH76p base.

[Lighting Board]

As FIG. 19 illustrates, lighting board 260 includes lighting circuitboard 261 and power supply board 262. For example, lighting board 260corresponds to controller 22 according to Embodiment 1, and is capableof simultaneously turning on lighting apparatuses.

Lighting circuit board 261 is a printed wiring board on which metallines are patterned. Lighting circuit board 261 includes a lightingcircuit for supplying power to light emitting unit 210. Specifically,metal lines and circuit elements (not illustrated) disposed on lightingcircuit board 261 form the lighting circuit.

Examples of the circuit elements include semiconductor elements such asa capacitor such as an electrolytic capacitor or a ceramic capacitor, aresistor, a coil element, a choke coil (choke transformer), a noisefilter, a diode, and an integrated circuit element. Many of the circuitelements are mounted on the main surface of lighting circuit board 261on the light emitting side (that is, on the light-transmissive member230 side).

As FIG. 19 illustrates, lighting circuit board 261 is a circular boardincluding ring-shaped opening 264, and includes larger-external diameterpart 261 a and smaller-external diameter part 261 b. Larger-externaldiameter part 261 a is larger in external diameter than smaller-externaldiameter part 261 b. Each of larger-external diameter part 261 a andsmaller-external diameter part 261 b has an approximately semicircularshape.

Larger-external diameter part 261 a includes connector 265. Connector265 is a connector for connecting wireless module 270.

Lighting circuit board 261 is held by housing 240 so as to be rotatableabout lamp axis J. In other words, lighting circuit board 261 isrotatable in accordance with the rotation of reflective member 220,light-transmissive member 230, and wireless module 270. Specifically,rotation of light-transmissive member 230 allows light-transmissivemember 230 and wireless module 270 which is connected to connector 265to be rotated in accordance with the rotation of light-transmissivemember 230.

Lighting circuit board 261 and light emitting unit 210 are connected by,for example, lead not illustrated. Here, since lighting circuit board261 is rotatable, the lead has a sufficient length to maintainconnection even if lighting circuit board 261 is rotated.

Power supply board 262 is a board for externally receiving power, and isa printed wiring board on which metal lines are patterned. Power supplyboard 262 is connected to power supply terminals 263. Power supply board262 supplies power supplied from power supply terminals 263, to lightingcircuit board 261. For example, power supply board 262 and lightingcircuit board 261 are electrically connected by a brush. Power supplyboard 262 is fixed to housing 240.

Each of power supply terminals 263 is an electrically conductive pin,and has a function to receive power for turning on light emitting unit210 from outside lighting apparatus 200. In other words, power supplyterminals 263 are electrical connecting pins for power supply.

For example, a pair of power supply terminals 263 receives predeterminedAC power from lighting fixture. Power supply terminals 263 supplies thereceived AC power to the lighting circuit via the metal lines and thebrush disposed on power supply board 262 and the metal lines disposed onlighting circuit board 261. A pair of power supply terminals 263 mayreceive two different DC powers instead of AC power.

Power supply terminals 263 also function as an attachment part forattaching lighting apparatus 200 to the lighting fixture. Specifically,lighting apparatus 200 is held by the lighting fixture by power supplyterminals 263 being connected to the socket of the lighting fixture.

As FIG. 18 illustrates, power supply terminals 263 are disposed so as toprotrude outward from the bottom of housing 240 (specifically,larger-diameter part 241). Specifically, power supply terminals 263 arepress-fitted into the through-hole of larger-diameter part 241 ofhousing 240 and fixed.

[Wireless Module]

Wireless module 270 is a communication unit for performing wirelesscommunication. Wireless module 270 is disposed in housing 240 such thatthe position of wireless module 270 is changeable. Details of changingthe position of wireless module 270 in housing 240 will be describedlater. Wireless module 270 performs wireless communication using, forexample, ZigBee (registered trademark), Bluetooth (registeredtrademark), or Wi-Fi (registered trademark).

FIG. 21A illustrates (a) a side view, (b) a front view, and (c) a bottomview of wireless module 270 according to Embodiment 3. FIG. 21Billustrates (a) a side view and (b) a front view of communicationcontrol board 274 included in wireless module 270 according toEmbodiment 3. FIG. 21C is a block diagram of a configuration of wirelessmodule 270 according to Embodiment 3.

As FIG. 21A and FIG. 21B illustrate, wireless module 270 includes resincase 271, connector 272, point light source 273, communication controlboard 274, and antenna 275.

Resin case 271 is a case for protecting communication control board 274and antenna 275. Resin case 271 has, for example, an approximatelycuboid shape, and covers communication control board 274 so as to exposeconnector 272.

Resin case 271 has a bottom surface (surface opposite to the connector272 side) including through-hole 271 a near point light source 273.Light emission of point light source 273 can be checked throughthrough-hole 271 a. In the case where resin case 271 haslight-transmissive properties, through-hole 271 a is not required.

Connector 272 is a connector for connecting to lighting circuit board261. Specifically, connector 272 is a female connector which isconnected to male connector 265 provided in lighting circuit board 261.Connection of connector 272 to connector 265 allows a signal which isbased on a wireless signal transmitted or received by antenna 275 to betransmitted to or received from the lighting circuit.

Point light source 273 is a light source having a lighting state whichchanges according to the strength of the received wireless signal. Forexample, point light source 273 is an LED. Point light source 273 emitsbrighter light with an increase in the radio field strength of thewireless signal received by antenna 275. Alternatively, point lightsource 273 emits light when the radio field strength of the wirelesssignal received by antenna 275 is greater than or equal to apredetermined threshold, and does not emit light when the strength isless than the threshold. The lighting state is not always required to bebrightness, but may be emission color. In other words, the emissioncolor may be changed according to the strength of the received wirelesssignal.

Accordingly, the communication state of wireless communication can bechecked by visually checking the lighting state of point light source273. For example, when changing the orientation of wireless module 270,point light source 273 emits bright light when wireless module 270 is inthe orientation where antenna 275 receives a wires signal accurately.

Communication control board 274 is a printed wiring board includingantenna 275. Specifically, communication control board 274 includes awireless control circuit such as an integrated circuit (IC) mountedthereon. As FIG. 18 illustrates, communication control board 274 isdisposed perpendicularly to board 211 of light emitting unit 210. Inother words, communication control board 274 is disposed perpendicularlyto the surface on which light emitting unit 210 is disposed (the surfaceof support base 250 on which light emitting unit 210 is disposed).Specifically, communication control board 274 is inserted tothrough-hole 226 of reflective member 220 so that antenna 275 is exposedto the reflective surface 225 side of reflective member 220.

As FIG. 21C illustrates, communication control board 274 includes, forexample, CPU 274 a, wireless driving circuit 274 b, and oscillators 274c and 274 d, as wireless control circuits.

For example, the wireless control circuit generates a control signal forswitching between turn-on and turn-off of light emitting unit 210 basedon the wireless signal received by antenna 275. The generated controlsignal is supplied to the lighting circuit of lighting circuit board 261via connectors 272 and 265, to switch between turn-on and turn-off oflight emitting unit 210.

The wireless signal is not limited to a signal for switching betweenturn-on and turn-off of light emitting unit 210. For example, thewireless signal may be a signal for dimming and adjusting color of lightemitted from light emitting unit 210.

Antenna 275 is a pattern antenna for transmitting or receiving awireless signal. In other words, antenna 275 includes wiring pattern(conductive pattern) disposed on communication control board 274.Disposing antenna 275 on communication control board 274 as a patternantenna leads to downsizing of antenna 275.

Antenna 275 may be an antenna for at least transmitting or receiving awireless signal, and is not limited to the pattern antenna. For example,antenna 275 may be a chip antenna.

In Embodiment 3, the frequency band of the wireless signal transmittedor received by antenna 275 is ultra high frequency (UHF) or super highfrequency (SHF).

In the case where wireless module 270 is inserted to through-hole 226 ofreflective member 220 to be connected to connector 265, antenna 275 isdisposed on reflective surface 225 side of reflective member 220. Inother words, antenna 275 is exposed to reflective surface 225 side ofreflective member 220. Since light-transmissive member 230 is made froma resin material which transmits radio waves, antenna 275 is capable oftransmitting or receiving the wireless signal even if reflective member220 and housing 240 are made from metal materials which block radiowaves.

[Change in Position of Wireless Module]

Wireless module 270 according to Embodiment 3 is disposed such that theposition of wireless module 270 is changeable. In other words, thepositions of communication control board 274 and antenna 275 arechangeable. Specifically, the positions of communication control board274 and antenna 275 are changeable in accordance with the change inposition of reflective member 220 and lighting board 260.

As described above, wireless module 270 is inserted to through-hole 226of reflective member 220 to be connected to connector 265 of lightingboard 260. In this state, reflective member 220 and lighting board 260are capable of rotating about lamp axis J serving as a rotary axis.Here, wireless module 270 is rotated in accordance with the rotation ofreflective member 220 and lighting board 260.

Accordingly, for example, as the white arrows in FIG. 17 illustrate,rotation of reflective member 220 allows the position (including theorientation) of wireless module 270 to be changed in housing 240.Accordingly, wireless module 270 can be disposed at a position withhigher received signal strength, leading to increased communicationquality of wireless communication.

Here, the position of wireless module 270 can be continuously changed byrotating reflective member 220. Accordingly, for example, in comparisonto the case where wireless module 270 can only be disposed at certainpositions as in Variation of Embodiment 3 to be described later, antenna275 can be disposed at a position with higher received signal strength.

[Conclusion]

As described above, lighting apparatus 200 according to Embodiment 3further includes housing 240 which houses light emitting unit 210.Wireless module 270 includes antenna 275 for transmitting or receiving awireless signal, and communication control board 274 including antenna275. The position of communication control board 274 is changeable inhousing 240.

With this, the position of communication control board 274 includingantenna 275 is changeable in housing 240. Accordingly, communicationcontrol board 274 can be disposed at a position which allows antenna 275to have a higher received signal strength. Hence, communication qualityof wireless communication can be increased. Since communication errorsand the like in wireless communication can be reduced, for example,lighting apparatuses 200 can be simultaneously turned on.

Moreover, for example, lighting apparatus 200 further includesreflective member 220 disposed in housing 240 and including reflectivesurface 225 which reflects light emitted from light emitting unit 210.Antenna 275 is disposed on reflective surface 225 side of reflectivemember 220.

With this, since antenna 275 is exposed to reflective surface 225 sideof reflective member 220, antenna 275 is capable of transmitting orreceiving a wireless signal even if reflective member 220 and housing240 are made from metal materials which block radio waves.

Moreover, for example, reflective member 220 includes through-hole 226into which communication control board 274 is insertable. Communicationcontrol board 274 is inserted to through-hole 226 so that antenna 275 isexposed to reflective surface 225 side.

With this, since antenna 275 is exposed to reflective surface 225 sideof reflective member 220, antenna 275 is capable of transmitting orreceiving a wireless signal even if reflective member 220 and housing240 are made from metal materials which block radio waves.

Moreover, for example, the position of reflective member 220 ischangeable in housing 240. The position of antenna 275 is changeable inaccordance with the change in position of reflective member 220.

This allows, for example, the position of antenna 275 to be changedwhile fixing communication control board 274 including antenna 275 toreflective member 220.

Moreover, for example, light emitting unit 210 is disposed on apredetermined surface, and communication control board 274 is disposedperpendicularly to the predetermined surface.

With this, antenna 275 is exposed from reflective member 220 such as ametal reflective plate or metallic plating, and thus, communicationquality of wireless communication can be increased in comparison to thestructure where an antenna is housed in housing 240.

Moreover, for example, communication control board 274 is a printedwiring board, and antenna 275 includes a wiring pattern disposed oncommunication control board 274.

Accordingly, antenna 275 and communication control board 274 can bedownsized.

Moreover, for example, wireless module 270 further includes point lightsource 273 having a lighting state which changes according to thestrength of a received wireless signal.

With this, the lighting state of point light source 273 is changedaccording to the strength of the received wireless signal, and thus,communication state of wireless communication can be checked by visuallychecking the lighting state of point light source 273. For example, whenchanging the orientation of wireless module 270, point light source 273emits bright light when wireless module 270 is in the orientation whereantenna 275 receives a wires signal accurately.

Embodiment 3 has described the example where reflective member 220includes one through-hole 226, but the present disclosure is not limitedto the example. Reflective member 220 may include a plurality ofthrough-holes 226. Here, lighting board 260 may include a plurality ofconnectors 265 positioned corresponding to the positions ofthrough-holes 226. With this, for example, wireless module 270 can beselectively inserted to one of through-holes 226, allowing selectiveconnection to a corresponding one of connectors 265. In other words, theposition of wireless module 270 is changeable.

In such a case, too, since wireless module 270 can be disposed at aposition which allows antenna 275 to have a higher received signalstrength, the communication quality of wireless communication can beincreased.

(Variation of Embodiment 3)

Next, Variation of Embodiment 3 will be described with reference to FIG.22A and FIG. 22B. FIG. 22A is a cross-sectional view of lightingapparatus 300 according to Variation of Embodiment 3. FIG. 22B is a planview of a layout of relay boards 360 included in lighting apparatus 300according to Variation of Embodiment 3.

Embodiment 3 has described the example where the position of antenna 275can be changed to an optimal position by rotating lighting board 260. InVariation of Embodiment 3, the position of antenna 275 is changed bychanging the position of lighting board 260.

As FIG. 22A illustrates, lighting apparatus 300 according to Variationof Embodiment 3 is different from lighting apparatus 200 illustrated inFIG. 18 in that relay board 360 and connector 361 are included insteadof lighting board 260.

Relay board 360 is a board which relays a signal between wireless module270 and an external lighting circuit. Relay board 360 is, for example, aprinted wiring board on which metal lines are patterned. As FIG. 22Billustrates, relay board 360 includes terminal group 362 and connector363.

Terminal group 362 includes a power supply terminal and a signalterminal. Terminal group 362 is a terminal for connecting to an externallighting circuit, and is connected to lead 364 as FIG. 22A illustrates.With this, terminal group 362 supplies power supplied from the externallighting circuit, to wireless module 270. Terminal group 362 allowstransmission and reception of a predetermined signal such as a turn-oninstruction between wireless module 270 and the external lightingcircuit.

Connector 363 is a connector for connecting wireless module 270.Connector 363 is, for example, the same as connector 272, and is afemale connector. For example, the turn-on instruction received bywireless module 270 is output to light emitting unit 210 via relay board360, lead 364, and connector 361.

In Variation of Embodiment 3, as FIG. 22B illustrates, relay board 360can be disposed at one of four positions. Specifically, housing 240 hasfour positions at which relay board 360 can be disposed. For example,relay board 360 is disposed by fitting into a recess or the likeprovided in housing 240.

The change in position of relay board 360 also changes the position ofwireless module 270. In other words, when the position of relay board360 is changed, the position of antenna 275 is also changed accordingly.

As described above, since the position of wireless module 270 ischangeable in housing 240 in Variation of Embodiment 3 as well, wirelessmodule 270 can be disposed at a position which allows antenna 275 tohave a higher received signal strength. Hence, the communication qualityof wireless communication can be increased. Since communication errorsand the like in wireless communication can be reduced, for example,lighting apparatuses 300 can be simultaneously turned on.

Embodiment 4

Next, a lighting apparatus according to Embodiment 4 will be described.

[Lighting Apparatus]

FIG. 23A is a cross-sectional view of lighting apparatus 500 accordingto Embodiment 4, and FIG. 23B is a top view of lighting apparatus 500.

As FIG. 23A and FIG. 23B illustrate, lighting apparatus 500 according toEmbodiment 4 is a sunken lighting apparatus, such as a recessed light,which emits light downward (toward the floor or a wall) by beinginstalled, for example, in ceiling 580 of a house. Lighting apparatus500 includes wireless communication function.

As FIG. 23A and FIG. 23B illustrate, lighting apparatus 500 includesfixture body 510, first housing 520 and second housing 570. Fixture body510 houses light emitting unit 530. First housing 520 houses lightingcircuit 535. Second housing 570 houses communication unit 575. Lightingapparatus 500 further includes attachment springs 540 and attachmentpart 550.

The following provides detailed descriptions of each structural memberincluded in lighting apparatus 500.

Light emitting unit 530 is a light emitting module which includes alight emitting element, and emits light of a predetermined color. InEmbodiment 4, light emitting unit 530 is a COB light-emitting module ora light emitting module including a surface mount device (SMD) element.

Fixture body 510 is a housing which houses light emitting unit 530, andhas, for example, an approximately truncated conical shape. Fixture body510 has an outer surface to which attachment springs 540 are attached. Aplurality of heat dissipating fins which project outward may be disposedon the outer surface of fixture body 510.

First housing 520 is a metal housing which houses lighting circuit 535.First housing 520 is formed by, for example, bending a metal platemember such as aluminum. First housing 520 has an approximately cuboidshape.

First housing 520 is disposed above a predetermined surface so as toform space 582 between first housing 520 and the predetermined surface.The predetermined surface is the top side of ceiling 580, that is, theback surface of ceiling 580.

Lighting circuit 535 supplies power which is for turning on lightemitting unit 530. Lighting circuit 535 is an example of a controllerwhich controls turn-on and turn-off of light emitting unit 530. Forexample, lighting circuit 535 executes the same functions as thoseexecuted by controller 22 according to Embodiment 1. Lighting circuit535 is connected to communication unit 575 in second housing 570 viacable 562.

Attachment springs 540 are fixed to the outer surface of fixture body510 so as to be biased outward. Attachment springs 540 are used forattaching lighting apparatus 500 (fixture body 510) to embedded hole581.

Attachment part 550 is connected to a cable (not illustrated) connectedto a grid power (commercial power) which is a supplier of AC power.Attachment part 550 supplies AC power obtained via the cable to lightingcircuit 535 in first housing 520 via cable 560. Attachment part 550 isdisposed on one lengthwise end of first housing 520.

Cable 560 is a cable for supplying the AC power received by attachmentpart 550, to lighting circuit 535 in first housing 520. Cable 561 is acable for lighting circuit 535 in first housing 520 to supply power tolight emitting unit 530 in fixture body 510. Cable 562 is a cable foroutputting, to lighting circuit 535 in first housing 520, a command suchas a turn-on instruction received by communication unit 575 in secondhousing 570.

Second housing 570 houses communication unit 575. Second housing 570 ismade from, for example, an electrically insulating resin material.Second housing 570 has, for example, an approximately cuboid shape.

As FIG. 23A and FIG. 23B illustrate, second housing 570 is disposedoutside fixture body 510 and first housing 520. Specifically, secondhousing 570 is disposed between fixture body 510 and first housing 520.

Communication unit 575 is, for example, wireless module 270 according toEmbodiment 3. In other words, communication unit 575 includes an antennato perform wireless communication. Specifically, communication unit 575executes the same functions as those executed by communication unit 23according to Embodiment 1. For example, communication unit 575 receivesa turn-on instruction by performing wireless communication with thecontrol device and the like. The received turn-on instruction is outputto lighting circuit 535 via cable 562.

[Return Loss of Antenna]

As described above, lighting apparatus 500 according to Embodiment 4 isattached to embedded hole 581 disposed in ceiling 580. Above theceiling, heat insulators, pipes and the like made from various materialsmay exist. In particular, in the case where the insulators, the pipesand the like are made from metal, the electric waves emitted fromcommunication unit 575 are absorbed by the metal, which may result indegraded communication quality.

The following describes various assumptions of environment above theceiling and measurement of return loss of communication unit 575 oflighting apparatus 500 under the assumed conditions.

FIG. 24 illustrates possible cases assumed in installation of lightingapparatus 500 according to Embodiment 4. Here, six cases (a) to (f) areassumed.

(a) indicates a case where no heat insulator is disposed above theceiling. In other words, (a) indicates a case where only lightingapparatus 500 (or lighting apparatus 500 and non-metal members) aredisposed above the ceiling.

(b) to (d) indicate cases where heat insulators are disposed above theceiling. In (b), glass fiber is used as a heat insulator. In (c), glassfiber with aluminum foil is used as a heat insulator. (d) assumes a casewhere glass fiber with aluminum foil is used as a heat insulator havinga thickness reduced due to aged degradation. Specifically, the reductionof thickness of the glass fiber with aluminum foil due to ageddegradation was achieved by compressing the glass fiber using a futoncompressing apparatus.

(e) assumes a case where a deck plate is present above the ceiling. (f)assumes a case where metal building materials such as pipes, wiring,ducts are present.

FIG. 25 illustrates results of measurement of return loss of lightingapparatus 500 according to Embodiment 4 based on the above six cases.FIG. 25 illustrates return loss of the antenna included in lightingapparatus 500 according to Embodiment 4 in the use of a wireless signalof 2.4 GHz band.

As FIG. 25 illustrates, in the use of a frequency of 2.4 GHz band,return loss is 0.1% or less except the case of (f) where metal buildingmaterials are present. In the case of (f), too, return loss is 0.2% orless. This means that sufficiently high-quality wireless communicationcan be performed.

Now, a lighting apparatus according to a comparative example ofEmbodiment 4 will be described with reference to FIG. 26. FIG. 26illustrates return loss of an antenna included in the lighting apparatusaccording to the comparative example of Embodiment 4 in the use of awireless signal of 2.4 GHz band.

In the lighting apparatus according to the comparative example, theantenna is attached to first hosing 520 without being covered. In otherwords, the lighting apparatus according to the comparative example doesnot include second housing 570.

As FIG. 26 illustrates, in the use of a frequency of 2.4 GHz band,return loss in the case of (f) is 0.6% approximately. Accordingly, ascan be understood from the comparison between FIG. 25 and FIG. 26, thesuppression effect of return loss according to Embodiment 4 isnoticeable particularly in the case of (f).

FIG. 27 illustrates return loss of the antenna included in lightingapparatus 500 according to Embodiment 4 in the use of a wireless signalof 920 MHz band. As FIG. 27 illustrates, in the use of a frequency of920 MHz band, return loss in the case of (f) is 0.7% approximately. Thisshows that it is preferable in Embodiment 4 that communication unit 575uses a frequency of 2.4 GHz band.

[Conclusion]

As described above, lighting apparatus 500 according to Embodiment 4further includes: fixture body 510 which houses light emitting unit 530,lighting circuit 535 which supplies power for turning on light emittingunit 530, first housing 520 which houses lighting circuit 535, andsecond housing 570 which houses communication unit 575. Second housing570 is disposed outside fixture body 510 and first housing 520.

Accordingly, disposing second housing 570 which houses communicationunit 575 outside first housing 520 which houses lighting circuit 535reduces return loss of the antenna, leading to increased communicationquality of wireless communication. Accordingly, since communicationerrors and the like in wireless communication can be reduced, forexample, lighting apparatuses 500 can be simultaneously turned on.

Moreover, for example, second housing 570 is disposed between fixturebody 510 and first housing 520.

Accordingly, disposing second housing 570 which houses communicationunit 575 between fixture body 510 which houses light emitting unit 530and first housing 520 which houses lighting circuit 535 reduces returnloss of the antenna, leading to increased communication quality ofwireless communication.

Moreover, for example, communication unit 575 performs wirelesscommunication using a frequency greater than or equal to 2.4 GHz.

Use of the frequency greater than or equal to 2.4 GHz increasescommunication quality of wireless communication.

(Variation of Embodiment 4)

Embodiment 4 has described the example where second housing 570 whichhouses communication unit 575 is disposed between fixture body 510 andfirst housing 520, but the present disclosure is not limited to theexample. The following describes Variations of Embodiment 4.

[Variation 1]

FIG. 28A is a cross-sectional view of lighting apparatus 600 accordingto Variation 1 of Embodiment 4, and FIG. 28B is a top view of lightingapparatus 600.

In Variation 1 of Embodiment 4, as FIG. 28A and FIG. 28B illustrate,second housing 570 is disposed in space 582 between first housing 520and ceiling 580. Communication unit 575 is connected to lighting circuit535 in first housing 520 via cable 562.

FIG. 29 and FIG. 30 each illustrate return loss of an antenna includedin lighting apparatus 600 according to Variation 1 of Embodiment 4 inthe use of a frequency of 2.4 GHz band and 920 MHz band.

As FIG. 29 illustrates, return loss in the use of a frequency of 2.4 GHzband is 0.2% or less in all cases of (a) to (f). Accordingly, lightingapparatus 600 according to Variation 1 of Embodiment 4 is capable ofperforming sufficiently high-quality wireless communication.

Moreover, as understood from the comparison with lighting apparatus 500illustrated in FIG. 25, lighting apparatus 600 according to Variation 1of Embodiment 4 has a lower return loss in the case of (f) where metalbuilding materials are present. With this, wireless communication withhigher quality can be performed by changing the position of secondhousing which houses communication unit 575 according to the environmentabove the ceiling where the lighting apparatus is disposed.

On the other hand, as FIG. 30 illustrates, in the use of a frequency of920 MHz band, return loss in the case of (f) is high similarly toEmbodiment 4. However, the return loss is 0.7% approximately inEmbodiment 4, whereas the return loss in Variation 1 of Embodiment 4 is0.6% or less, which shows improvement in communication quality.Accordingly, in the case of (f), for example, communication quality ofwireless communication can be increased by disposing second housing 570in space 582 between first housing 520 and ceiling 580.

As described, in lighting apparatus 600 according to Variation 1 ofEmbodiment 4, for example, first housing 520 is disposed above apredetermined surface so as to form space 582 between first housing 520and the predetermined surface, and second housing 570 is disposed inspace 582.

This increases communication quality of wireless communication.

[Variation 2]

FIG. 31 is a cross-sectional view of lighting apparatus 700 according toVariation 2 of Embodiment 4.

In Variation 2 of Embodiment 4, as FIG. 31 illustrates, lightingapparatus 700 includes plate 771 made from an electrically insulatingmaterial, and movable part 772 which movably connects plate 771 to aportion of first housing 520.

Plate 771 is connected to the bottom side of first housing 520 viamovable part 772. When first housing 520 is disposed above thepredetermined surface, plate 771 is fixed to the predetermined surface.Furthermore, second housing 570 which houses communication unit 575 isattached to plate 771.

In Variation 2 of Embodiment 4, plate 771 is pivotally connected to anend portion of the bottom of first housing 520 about movable part 772.For example, the crosswise direction of the bottom of first housing 520(specifically, the direction orthogonal to the drawing sheet of FIG. 31)is the axial direction of the pivot. Plate 771 is pivotable such thatplate 771 departs from the bottom of first housing 520. Accordingly, bycausing plate 771 to pivot according to the size of space 582 betweenfirst housing 520 and ceiling 580, plate 771 can be brought into contactwith the predetermined surface of ceiling 580.

As described above, lighting apparatus 700 according to Variation 2 ofEmbodiment 4 further includes, for example, plate 771 made from anelectrically insulating material, and movable part 772 movablyconnecting plate 771 to a portion of first housing 520. Plate 771 isfixed to the predetermined surface when first housing 520 is disposedabove the predetermined surface, and second housing 570 is attached toplate 771.

Accordingly, the positional relationship between first housing 520 andsecond housing 570 can be easily changed by moving plate 771. Thisfacilitates installation of lighting apparatus 700.

Variation 2 of Embodiment 4 has described the example where plate 771 isrotatable about the crosswise direction of the bottom surface of firsthousing 520. Plate 771 may be rotatable about the directionperpendicular to the bottom surface of first housing 520 (or thicknessdirection of ceiling 580). This facilitates installation t of lightingapparatus 700.

[Variation 3]

FIG. 32 is a cross-sectional view of lighting apparatus 800 according toVariation 3 of Embodiment 4.

In Variation 3, second housing 570 which houses communication unit 575is disposed in contact with a side surface of fixture body 510.

For example, second housing 570 is bonded to a side surface of fixturebody 510 by an adhesive or the like. Alternatively, second housing 570may be disposed on a predetermined surface of fixture body 510, or maybe inserted to a recess disposed on a side surface of fixture body 510.Second housing 570 may be attached to fixture body 510 in any methods.

Accordingly, even when, for example, ceiling 580 includes metal buildingmaterials, communication unit 575 is capable of performing wirelesscommunication using embedded hole 581 of ceiling 580. Here, since secondhousing 570 is disposed in contact with a side surface of fixture body510, second housing 570 is disposed approximately immediately aboveembedded hole 581. Hence, communication quality of wirelesscommunication can be increased.

(Others)

Although the lighting apparatus and the lighting system according to thepresent disclosure have been described based on the embodiments andtheir variations, the present disclosure is not limited to theseembodiments and variations.

For example, the above embodiments have described the examples where theantenna is mounted on a printed wiring board, but the antenna accordingto the present disclosure is not limited to the examples. The antennamay be a dipole antenna.

Embodiments 2 to 4 and their variations may be implemented independentlyof Embodiment 1. In other words, Embodiments 2 to 4 and their variationsmay be implemented as a structure not including the structural elementsrecited in independent claims which indicate the broadest concepts ofthe present disclosure. For example, wireless module 270 according toEmbodiment 3 may simply perform control of turn-on and turn-off of lightemitting unit 210, and is not required to perform control forsimultaneous turn-on according to Embodiment 1.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that they may be appliedin numerous applications, only some of which have been described herein.It is intended by the following claims to claim any and allmodifications and variations that fall within the true scope of thepresent teachings.

What is claimed is:
 1. A lighting apparatus which is one of a pluralityof lighting apparatuses each capable of performing wirelesscommunication with a device, the lighting apparatus comprising: a lightemitting unit; a controller which controls turn-on of the light emittingunit; and a communication unit configured to perform wirelesscommunication with the device to obtain a correction time from thedevice, the correction time being based on communication delay betweenthe device and each of the plurality of lighting apparatuses, whereinthe communication unit is further configured to obtain a turn-oninstruction for turning on the light emitting unit from the device, andto transmit a response to the turn-on instruction to the device byperforming carrier sense, upon obtainment of the turn-on instruction,the controller calculates a standby time by subtracting a communicationlatency from the correction time, after the response is transmitted tothe device, the communication latency being a period taken from when theturn-on instruction is obtained to when the carrier sense issuccessfully performed and the response is transmitted to the device,and the controller turns on the light emitting unit after passage of thestandby time from when the response is transmitted to the device.
 2. Thelighting apparatus according to claim 1, wherein the device and theplurality of lighting apparatuses are connected in a star topology, andthe device transmits the turn-on instruction to the plurality oflighting apparatuses using multicast.
 3. The lighting apparatusaccording to claim 1, wherein the communication unit is capable ofperforming wireless communication with another one of the plurality oflighting apparatuses.
 4. The lighting apparatus according to claim 1,wherein the plurality of lighting apparatuses are located within a 30 mradius from the device.
 5. The lighting apparatus according to claim 1,wherein the correction time is calculated based on a communication timebetween the device and a lighting apparatus requiring a longestcommunication time among the plurality of lighting apparatuses.
 6. Thelighting apparatus according to claim 1, wherein the communication unitis configured to perform the wireless communication using only apredetermined frequency.
 7. The lighting apparatus according to claim 1,wherein the communication unit is configured to perform the wirelesscommunication using a frequency ranging from 421 MHz to 2483.5 MHz,inclusive.
 8. The lighting apparatus according to claim 1, furthercomprising a housing which houses the light emitting unit, wherein thecommunication unit includes: an antenna for either one of transmittingand receiving a wireless signal; and a communication control boardincluding the antenna, and a position of the communication control boardis changeable in the housing.
 9. The lighting apparatus according toclaim 8, further comprising a reflective member disposed in the housingand having a reflective surface which reflects light emitted from thelight emitting unit, wherein the antenna is disposed on a reflectivesurface side of the reflective member.
 10. The lighting apparatusaccording to claim 9, wherein the reflective member includes one or morethrough-holes through which the communication control board isinsertable, and the communication control board is inserted into one ofthe one or more through-holes so as to expose the antenna on thereflective surface side.
 11. The lighting apparatus according to claim10, wherein a position of the reflective member is changeable in thehousing, and a position of the antenna is changeable in accordance witha change in position of the reflective member.
 12. The lightingapparatus according to claim 8, wherein the light emitting unit isdisposed on a predetermined surface, and the communication control boardis disposed perpendicularly to the predetermined surface.
 13. Thelighting apparatus according to claim 8, wherein the communicationcontrol board is a printed wiring board, and the antenna includes awiring pattern disposed on the communication control board.
 14. Thelighting apparatus according to claim 8, wherein the communication unitfurther includes a light source having a lighting state which changesaccording to a strength of the wireless signal received.
 15. Thelighting apparatus according to claim 1, further comprising a fixturebody which houses the light emitting unit; a lighting circuit whichsupplies electric power for turning on the light emitting unit; a firsthousing which houses the lighting circuit; and a second housing whichhouses the communication unit, wherein the second housing is disposedoutside the fixture body and the first housing.
 16. The lightingapparatus according to claim 15, wherein the first housing is disposedabove a predetermined surface so as to form a space between the firsthousing and the predetermined surface, and the second housing isdisposed in the space.
 17. The lighting apparatus according to claim 16,further comprising: a plate comprising an electrically insulatingmaterial; and a movable part which movably connects the plate to aportion of the first housing, wherein the plate is fixed to thepredetermined surface when the first housing is disposed above thepredetermined surface, and the second housing is attached to the plate.18. The lighting apparatus according to claim 15, wherein the secondhousing is disposed between the fixture body and the first housing. 19.The lighting apparatus according to claim 18, wherein the second housingis disposed in contact with a side surface of the fixture body.
 20. Thelighting apparatus according to claim 15, wherein the communication unitis configured to perform the wireless communication using a frequencygreater than or equal to 2.4 GHz.
 21. A lighting system comprising: adevice; and a plurality of lighting apparatuses each capable ofperforming wireless communication with the device, wherein the deviceincludes: a correction time calculator which calculates a correctiontime which is based on communication delay between the device and eachof the plurality of lighting apparatuses; and a first communication unitconfigured to perform wireless communication with the plurality oflighting apparatuses to transmit, to the plurality of lightingapparatuses, the correction time and a turn-on instruction for turningon the plurality of lighting apparatuses, each of the plurality oflighting apparatuses includes: a light emitting unit; a controller whichcontrols turn-on of the light emitting unit; and a second communicationunit configured to obtain the correction time and the turn-oninstruction from the device, and to transmit a response to the turn-oninstruction to the device by performing carrier sense, upon obtainmentof the turn-on instruction, the controller calculates a standby time bysubtracting a communication latency from the correction time, after theresponse is transmitted to the device, the communication latency being aperiod taken from when the turn-on instruction is obtained to when thecarrier sense is successfully performed and the response is transmittedto the device, and the controller turns on the light emitting unit afterpassage of the standby time from when the response is transmitted to thedevice.